(a) Field of the Invention
The present invention relates to a liquid crystal display apparatus.
(b) Description of the Related Art
A liquid crystal display (“LCD”) apparatus is one of the most widely used flat panel display apparatuses. The LCD apparatus includes two panels (e.g., a lower panel and an upper panel) each having electric field generating electrodes, such as pixel electrodes and a common electrode, and a liquid crystal (“LC”) layer interposed therebetween. The LCD apparatus displays an image by applying a voltage to the electric field generating electrodes to generate an electric field in the LC layer which determines alignment of LC molecules in the LC layer to control polarization of incident light.
Among such LCD apparatuses, a vertical alignment (VA) mode LCD, which aligns LC molecules such that the long axes of the LC molecules are perpendicular to the panels in the absence of electric field, is spotlighted because of the high contrast ratio and wide reference viewing angle obtained with the VA mode LCD. Here, the reference viewing angle means a viewing angle having a contrast ratio of 1:10 or an effective angle in inversion of brightness between grayscales.
The wide viewing angle of the VA mode LCD can be realized by protrusions on and/or cut portions in the field-generating electrodes. Since the direction in which the liquid crystal molecules are tilted can be determined by the use of the cut portions and the protrusions, the reference viewing angle can be widened by variously arranging the cut portions and the protrusions to distribute the tilt direction of the liquid crystal molecules in various directions.
However, the VA mode LCD has poor lateral visibility as compared with front visibility. For example, in a case of an LCD apparatus with a patterned vertical alignment (“PVA”) mode having the cut portions, an image becomes brighter at the sides thereof, and in some cases the difference in brightness between high grayscales may disappear making the profile of the image vague.
To improve the lateral visibility, a conventional method includes dividing a pixel into two sub-pixels capacitively coupled to each other. One of the two sub-pixels is directly supplied with a voltage, while the other is subjected to a voltage drop by the capacitive coupling such that the two sub-pixels have different voltages, and therefore, cause different transmittances of light incident on the LC layer.
However, the conventional method may not control the transmittances of the two sub-pixels. In a high resolution LCD apparatus, one horizontal period (1 H) is shortened in the conventional method, so that a charging margin of pixels is reduced. In addition, when a frame frequency increases, for example when the frame frequency is 120 Hz, the one horizontal period (1 H) is extremely short, such that the image signal cannot be displayed.
In addition, if the two divided sub-pixels have openings having different shapes, optical characteristics at front and side surfaces are different from each other and thus deterioration in image quality results.